Abstracts (poster) - Wissenschaft Online

Peter Hemmerich, Stefanie Weidtkamp-Peters, Christian Hoischen, Lars Schmiedeberg,
Indri Erliandri, Stephan Diekmann
CENP-I as a new epigentic mark at centromere chromatin
Epigenetic marking of a DNA locus may be realized by posttranslational modifications of
nucleosomal histones or by stable binding of a specific protein at that locus. Centromere
identity is believed to be conveyed by CENP-A, a specialized histone H3 analog that
substitutes canonical H3 within centromeric nucleosomes. CENP-A is constitutively
present at centromeres and required for the association of all other kinetochore proteins.
To test whether these epigenetic properties are unique to CENP-A we have assessed the
exchange rates of inner centromere proteins by quantitative microscopy throughout the
cell cycle in living human cells (1). We demonstrate that, in addition to CENP-A, CENP-I
is also a stable centromere component that does at no time exchange with soluble pools
at centromeres. Loading of CENP-I onto centromeric chromatin occurs co-replicationally,
while CENP-A is loaded in early G1. A subfraction of CENP-H (~20%) also stays stably
bound to centromeres throughout the cell cyle. In contrast, CENP-B, CENP-C, and
hMis12 turn over completely at centromeres with residence times ranging between
seconds to hours. Our data reveal a wide range of cell cycle-specific assembly plasticity
of the centromere during the cell-cycle and identify CENP-I as a potentially additional
epigentic marker at centromeres.
Literature
(1) Hemmerich et al., J. Cell Biol. (2008) in press
contact:
PhD Peter Hemmerich
Leibniz Institute for Age Research
Fritz-Lipmann-Institute
phemmer@fli-leibniz.de
Beutenbergstr. 11
07745 Jena (Germany)